Perception intensity estimates of audio signals have been the subject of research for decades. Although audio signal processing and acoustic engineering have reached significant progress with respect to different aspects of recording, engineering, storage and reproduction many key issues have been left as they originally were, namely aspects which were to be dealt with on the basis of subjective analysis of the skilled sound engineer. This manual approach to several key issues is, of course, acceptable to the degree that the individual preference of the recipient, i.e. the listener, determines the individual opinion of the quality of the perceived audio signal.
For different purposes it would, however, be advantageous if a more automated approach to the processing of audio signal was possible. One of these purposes is loudness estimates, which relate to the different listeners' perception of how loud a present signal is. An automated loudness estimation of audio signals is highly needed for different purposes such as automatic gain control in relation to broadcasting or, e.g., reproduction of audio signals in a car.
A problem related to measuring of loudness is that it for many years has been well accepted that the loudness perception of an audio signal is not just a straightforward measurement and a subsequent processing of an audio signal to be evaluated.
A more advanced example of loudness estimation is disclosed in US 2004/0044525 A1 where loudness estimation is based on the assumption that loudness of speech must be evaluated differently than other audio signal components. A problem of the disclosed method is that a signal to be evaluated initially must be processed for the purpose of identifying and separating speech components, which is a relatively complicated and processing consuming affair.
It is the object of the invention to obtain a relatively straightforward and universal loudness evaluation and estimation, which may also serve as the basis for automated gain control.